1. Field of the Invention
The present invention relates to a method of operating a boiling water reactor (hereinafter referred to as "BWR") plant and to a BWR plant, and more particularly to a method of operating a BWR plant and to a BWR plant with both of which the radioactive concentration level during the operation can be reduced or the exposure dose at the time of handling the nuclear fuel rod can be reduced.
2. Background of the Invention
In a BWR plant, nickel and cobalt corrosion products in the form of ions are generated from structural material of a feed and condensed water system, the corrosion products being deposited to a nuclear fuel rod and activated. The radioactive nuclei are dissolved from the nuclear fuel rod and deposited onto the reactor core structural materials and primary coolant piping. As a result, the exposure rate during the periodical inspection increases. In order to prevent this, in a conventional technology the injection of iron crud is effected. By making use of a fact that the radioactive ions are fixed when a ferrite is formed, the concentration of the radioactive ions has been decreased. A conventional technology of the foregoing type has been disclosed in Japanese Patent Laid-Open No. 60-78390.
However, in the conventional technique, a large quantity of crud is deposited to the nuclear fuel rod, causing the following problems at the time of treating the spent nuclear fuel rod.
First, a large quantity of waste occurs in a decontamination working, which is performed in a power plant for the purpose of transporting the spent nuclear fuel rod to a reprocessing plant. Further, the exposure dose for operators increases.
The iron acts as an interfering substance in the fuel reprocessing process.
A second problem is that the radioactive ions in the reactor water cannot be reduced satisfactorily and the concentration of the iron crud in the reactor core is increased. As a part of iron crud contain radioactive nucleid, high concentration of iron crud becomes radiation source as a radioactive precipitate.